Towing a trailer is a skill that requires hours of practice to acquire. When a vehicle operator who has not yet acquired the skill, such as someone who rents a trailer on a weekend to move some large items, tries to tow a trailer, the vehicle and/or trailer may get damaged when the trailer jack-knifes, a situation which occurs when the trailer pivots at a large angle with respect to the vehicle during a backing up operation. It may be too late when the operator realizes the mistake. To prevent such an occurrence, a device is needed to warn the operator of a potential jack-knife situation, thereby avoiding damage to the vehicle and/or trailer.